Passive optical test termination

Abstract

An optical test termination device ( 100 ) for use in optical network comprising a passive optical element ( 102 ) and a first optical coupler ( 104 ) and a second optical coupler ( 106 ) for coupling the optical test termination device ( 100 ) to an optical fiber ( 108, 110, 202 ). The passive optical element ( 102 ) comprises an input for receiving a test signal from the network and an output for outputting a response signal towards the network, wherein in response to the test signal the passive optical element ( 102 ) is operable to output the response signal, wherein said response signal differs from said test signal.

1. An optical test termination device for use in an optical network, comprising:
 a first optical coupler and a second optical coupler configured to couple the optical test termination device to an optical fiber; 
 a passive optical element comprising
 an input configured to receive a test signal from the network; 
 an output configured to output a response signal towards the network; 
 an optical delay line; and 
 an optically controlled optical switch; 
 
 wherein the passive optical element is configured to output the response signal responsive to receiving the test signal, the response signal having a length that is different than a length of the test signal. 
 
     
     
       2. The device of  claim 1  wherein the passive optical element is configured to output the response signal to carry a message that is different from a message carried by the test signal. 
     
     
       3. The device of  claim 1  wherein a switch-off time of the optically controlled optical switch is less than a switch-on time of the optically controlled optical switch. 
     
     
       4. The device of  claim 1  further comprising an electrically controlled optical switch configured to switch off the response signal during normal operation. 
     
     
       5. A communications network in which at least a part of the network is an optical network configured to carry optical signals over optical fibers, the network comprising:
 at least one optical fiber to communicate optical signals; and 
 an optical test termination device comprising:
 a first optical coupler and a second optical coupler configured to couple the optical test termination device to one or more optical fibers; 
 a passive optical element comprising
 an input configured to receive a test signal from the network; 
 an output configured to output a response signal towards the network; 
 an optical delay line; and 
 an optically controlled optical switch; 
 
 wherein the passive optical element is configured to output the response signal responsive to receiving the test signal, the response signal having a length different than a length of the test signal. 
 
 
     
     
       6. The network of  claim 5  wherein the first optical coupler is configured to connect the input of the passive optical element to a downstream optical fiber, and wherein the second optical coupler is configured to connect the output of the passive optical element to an upstream optical fiber. 
     
     
       7. The network of  claim 5  wherein the first optical coupler is configured to connect the input of the passive optical element to an optical fiber on a network side, and wherein the second optical coupler is configured to connect the output of the passive optical element to the same optical fiber on a subscriber side. 
     
     
       8. The network of  claim 7  further comprising a receiver disposed on the network side of the optical fiber from the optical test termination device, the receiver configured to receive response signals and normal operation signals. 
     
     
       9. The network of  claim 8  further comprising a separator disposed on the network side of the optical fiber from the optical test termination device, the separator configured to separate the response signals from the normal operation signals. 
     
     
       10. The network of  claim 9  further comprising:
 a first receiver configured to receive the response signals; and 
 a second receiver configured to receive the normal operation signals. 
 
     
     
       11. The network of  claim 5  wherein a switch-off time of the optically controlled optical switch is less than a switch-on time of the optically controlled optical switch. 
     
     
       12. The network of  claim 5  further comprising an electrically controlled optical switch configured to switch off the response signal during normal operation. 
     
     
       13. The network of  claim 5  wherein the passive optical element is configured to output the response signal to carry a message that is different from a message carried by the test signal. 
     
     
       14. A method of testing a termination of an optical network, the method comprising:
 transmitting a test signal towards a termination of an optical network; 
 receiving the test signal at a passive optical element connected to the termination of the optical network, the passive optical element comprising an optical delay line and an optically controlled optical switch; and 
 transmitting a response signal from the passive optical element towards the optical network responsive to receiving the test signal, a length of a response signal being different than a length of the received test signal.